Overspeed control for hydraulic turbines



Sept 1937. R- E. B. SHARP 2,094,282

OV ERSPEED CONTROL FOR HYDRAULIC TURBINES Filed Sept. 28, 1935 2 SheetsSheet 1 INVENTQR E f 5- harp R. E. B. SHARP 2,094,282 OVERSPEED CONTROL FOR HYDRAULIC TURBINES I Filed Sept. 2a, 1955 2 Sheets-Sheet 2 Sept. 28, 1937.

INVENTOR 5. Ska/,0

VIII I Patented Sept. 28, 1937 OVERSPEED CONTROL FOR HYDRAULIC TURBINES Robert E. Brunswick Sharp, Philadelphia, Pa., assignor to Baldwin-Southwark Corporation, a corporation of Delaware Application September 28, 1935, Serial No. 42,590

3 Claims.

This invention relates generally to improved apparatus for reducing the runaway speed of hydraulic turbines, particularly low head adjustable runner blade turbines.

It is one object of my invention to provide improved means for controlling the runaway speed of a hydraulic turbine by automatically controlling the effective head on the runner independently of the position or adjustment of the gates or runner blades in case an adjustable blade propeller type turbine is employed. A further and more specific object is to provide improved means having the foregoing mode of operation and adapted not to interfere with flow conditions through the turbine during normal operation thereof.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. 1 is a partial sectional view of a hydraulic turbine of the horizontal type employing my improved overspeed control;

Fig. 2 is an enlarged sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a sectional View of a vertical axis turbine employing my invention;

Fig. 4 is an enlarged sectional view of a solenoid controlled air valve employed in my improved combination.

In the particular embodiments of the invention which are disclosed herein merely for the [purpose of illustrating certain specific forms among possible others that the invention might take in practice, I have shown in Fig. 1 a conventional type of horizontal hydraulic turbine having a turbine runner l which may be of the Francis, propelleror other type connected to a shaft 2 for driving a generator 3. As is usual in the form of turbine setting shown, the headwater is indicated at 4 and tailwater at 5, these being con nected by a suitable inlet 6 and draft tube or discharge passage 1. The details of construction of the apparatus above mentioned are well-known and may be of various well-known types, and hence the same need not be described in further detail.

One element of my improved speed reducing apparatus comprises an air inlet pipe 8 having a lateral pipe 9 which terminates in the draft tube 1 preferably at a point spaced inwardly from the inner Wall thereof. Pipe 9 as shown in Fig. 2 is preferably stream-lined in the direction of flow through the draft tube and is preferably slightly angularly disposed to conform to the whirling component of the water as it leaves the runner during normal operation. The entrance end of pipe 8, Fig. 4, is provided with a valve H! which may be of the flap valve type pivoted at ll and held in its normal horizontal closed position by a latch l2. This latch may be controlled in any suitable manner but for purposes of illustration a solenoid I3 is provided. The solenoid is connected to a suitable power source though lines l4 and is controlled by any suitable speed responsive means diagrammatically shown for purposes of illustration as a centrifugal flyball governor l5 driven by the turbine through its shaft 2. The circuit for the solenoid be connected to any suitable contacts l6 adapted to be closed by a governor operated sleeve il moved axially by the governor flyballs whereby when a predetermined excess speed is reached, collar ll will engage contact IB and close the circuit for the solenoid, thereby releasing latch 22 and permitting inlet valve ID to fall open by gravity. Air is thereupon admitted through pipes 8 and 9 to the draft tube with the result that any vacuum therein is broken. This results in a substantial reduction of the effective head from H1 to Hz, Fig. l, and thus reduces or limits the runaway speed of the runner.

Under excess speed conditions, the water leaves the runner with a large whirl component which causes the water to hug the Wall of draft tube 1. To overcome this condition, pipe 9 projects a suflicient distance inwardly of the draft tube wall to admit air to a more central portion of the draft tube, at least inside the zone of the more pronounced whirl in the water. Valve I0 may be manually reset upon restoration of normal conditions. The invention is particularly applicable to syphon settings although it is equally applicable to other settings as shown in the vertical axis turbine of Fig. 3, wherein the parts are given the same reference numbers as in Fig. 1.

From the foregoing disclosure, it is seen that I have provided a new and improved means for automatically reducing the runaway speed of a hydraulic turbine by positively reducing the effective head thereon but without the necessity of relying upon adjustment of the turbine gates or runner blades. Hence the component elements of the invention are simple in construction, operation and maintenance and are highly effective in producing the desired control of the runaway conditions automatically upon occurrence thereof.

It will of course be understood that various changes in details of construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the in- V vention as set forth in the appended claims.

ing normal speed, and means for controlling said 7 valve so that it is completely open automatically onlyupon occurrence of a predetermined speed i Y above normal and is thereafter independent of any further degree of speed. V

2. The combination set forth in claiml further characterized in that said valve has provision for being reclosed only by manual operation after it is once opened. 7

.3. The combination set forth inclaim 1 further characterized in that said air passage extends inwardly of the draft tube beyond the wall thereof so-as to be free of the excessive plural component 10 of the water during overspeed operation.

' ROBERT E. BRUNSWICK SHARP. 

